United States Department of Transportation
i
Field performance of RAS test sections and laboratory investigation of impact of rejuvenators on engineering properties of RAP/RAS mixes.
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2014-04-01
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[PDF-2.28 MB]
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Abstract:In the last several years, recycled asphalt shingles (RAS), in addition to reclaimed asphalt pavement (RAP),
have been widely used in Texas. The use of RAS can significantly reduce the cost of asphalt mixtures, conserve
energy, and protect the environment. However, one of the major concerns is poor cracking resistance of RAS mixes
due to super stiff asphalt binder in the RAS. This research focused on field performance of RAS test sections and
the benefit of using rejuvenators in improving cracking resistance of RAS(/RAP) mixes. In addition, a simple cost
analysis was performed to investigate the cost-benefits of using rejuvenators. It was found that both increasing
design density (leading to higher virgin binder content) and using soft virgin binders (e.g. PGXX-28) can improve
cracking resistance. With respect to improving cracking resistance of RAS mixes, the three rejuvenators evaluated
in this research are all effective. Furthermore, the incorporation of rejuvenators also improved the moisture
susceptibility and rutting resistance of the mixtures containing recycled materials. Apparently, additional tests and
analyses are necessary. Specifically, field test sections with different types of rejuvenators should be constructed
for further evaluation.
Additionally, the observed field performance indicated that cracking performance is influenced by many
factors, such as traffic, climate, existing pavement conditions for asphalt overlays, and pavement structure and layer
thickness. It is extremely difficult to propose a single cracking requirement for all applications. There is a need to
develop a RAP/RAS mix design and performance evaluation system for project-specific service conditions,
including traffic, climate, existing pavement conditions, etc.
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